JP2574529B2 - Carbon containing refractories - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a carbon-containing refractory having extremely excellent oxidation resistance.

[Related Art] A refractory composition containing a carbonaceous material such as graphite has other properties due to its high thermal conductivity, the property of preventing leakage of molten metal and slag, and the property of preventing refractory from excessive sintering. In coexistence with refractory aggregates, it complements the advantages of refractory aggregates and is widely used as a refractory for metallurgy, such as refractories for iron making and steel making.

However, carbonaceous materials such as graphite are very easily oxidized in an oxidizing atmosphere, and lose the above-mentioned advantages. Therefore, in order to further demonstrate the advantages of carbon-containing refractories, carbonaceous materials such as graphite must be used. It is extremely important in practical use to minimize oxidation, that is, to provide a carbon-containing refractory having excellent oxidation resistance.

The present inventors have proposed a method for imparting oxidation resistance to a carbonaceous material, as described in JP-A-1-249645, by using graphite as an SiO ₂ system, an Al ₂ O ₃ system, a TiO ₂ system, and a ZrO ₂ system. The application of a coating by a colloidal solution of the system has already been disclosed.

In some cases, nitrides, borides, carbides, and metal powders are simply added to carbon-containing refractories to improve the oxidation resistance of carbon in the refractories. However, the bonding strength between aggregates is low.
In the range of 0 to 1000 ° C., there are many open pores, and the effect of improving oxidation resistance is small.

In addition, although the purpose is different, in an amorphous refractory using water, an amorphous refractory using aluminum powder coated with a resin in advance to easily undergo hydrolysis by water (Japanese Patent Publication No. 58-49511) Amorphous refractories using pitch-coated silicon nitride in which fine pitches of silicon nitride are coated with tar pitch are also disclosed (JP-A-2-80378). These refractories have the same effect as the carbon-containing refractories of the present invention. Are different.

[Problem to be Solved by the Invention] Japanese Patent Application Laid-Open No. 1-249645 discloses that an oxide-based material is used as a coating material, and graphite particles (hereinafter, graphite particles are used as a typical example of carbonaceous particles). ) Each is excellent in improving the oxidation resistance, but in the high temperature range of 1500 ° C or higher, part of the graphite may be oxidized and consumed by the oxidation-reduction reaction between the coating material and the graphite particles. Absent.

In addition, there is an example in which a nitride, a boride, a carbide, and a metal powder are simply added as an antioxidant to improve oxidation resistance.However, since phenol resin is used as a binder, 400 to 1000 ° C. The bonding strength between the aggregates constituting the refractory in the above temperature range is low and there are many open pores. For this reason 400-1
Antioxidation at 000 ° C is not sufficiently exhibited.

[Means for Solving the Problems] The present inventors have further developed a coating material of graphite particles, and have developed a coating material having excellent oxidation resistance at high temperatures (1500 ° C. or higher).

Further, the present inventors have found that the coating material is made into a fine powder and added to the carbon-containing refractory to provide a more excellent anti-oxidation effect as compared with a conventional carbon-containing refractory simply added with an antioxidant.

That is, the present invention relates to 10 to 300 parts by weight of one or more fine powders selected from the group consisting of nitrides, carbides or borides other than boron carbide, metals and alloys in advance per 100 parts by weight of the high softening point pitch. The present invention relates to a carbon-containing refractory comprising 3 to 50 parts by weight of a carbonaceous substance coated with a coating material having an addition ratio of 50 to 97 parts by weight.

[Action] A high softening point pitch having a residual carbon ratio of 50% or more and a softening temperature of 100 to 400 ° C. was selected as a component of a coating material having no redox reaction at high temperature and excellent in leaking properties with graphite. Residual coal rate 50
The reason why it is determined to be at least% is that the low carbon residue has a high volatile content, so that the pitch coated on the graphite particles volatilizes during the heating to form a uniform coating layer, and the residual carbon ratio is high. This is because a more uniform coating layer can be easily formed.

The reason for setting the softening temperature to 100 to 400 ° C is that the softening temperature is 10
When the temperature is lower than 0 ° C., the fluidity of the pitch during the heating increases, the filling property of the refractory decreases, and the oxidation resistance and the corrosion resistance decrease. Conversely, when the softening temperature is a high softening point pitch exceeding 400 ° C., the fluidity is poor and it is difficult to form a coating having a uniform thickness.

Next, nitride (Ti) is placed in such a high softening point pitch.
N, Si ₃ N ₄ etc.), boride (BN etc.), carbide (TiC, SiC etc.)
And fine powders of metals and alloys (Al, Si, Al-Si, Al-Mg
And the like, the effect of mixing one or two or more kinds of fine powders selected from the above.

By adding these fine powders, the residual carbon ratio and oxidation resistance of the carbonized pitch are improved. This is considered to be due to the effect of the added fine powder trapping foreign oxidizing gas. Further, it should be noted that the pitch in which the fine powder is mixed has a large strength developing effect. This is considered to be because the density of the carbonized pitch is increased by the fine powder trapping the gas component. In other words, it is a synergistic effect of high softening pitch and fine powder.The carbon-containing refractory using graphite coated with this coating material is compared with the refractory to which fine powder as antioxidant and high softening pitch are individually added. It has excellent oxidation resistance and corrosion resistance, and has higher strength characteristics.

The coating material for coating the carbonaceous substance is composed of the high softening point pitch and the fine powder,
The compounding ratio is in the range of 10 to 300 parts by weight of the fine powder per 100 parts by weight of the high softening point pitch. The amount of fine powder is 1
If the amount is less than 0 part by weight, it is not preferable because the effect of using the fine powder is small. On the other hand, if it exceeds 300 parts by weight, the amount of the fine powder becomes excessive, and it is not preferable because a coating in a good dispersed state cannot be applied.

The coating amount of the coating material on the carbonaceous material is about 3 to 30 parts by weight based on 100 parts by weight of the carbonaceous material. A coating amount of less than 3 parts by weight is not preferable because the coating effect is small, and a coating amount of more than 30 parts by weight is unfavorable because the quality such as poor filling is rather deteriorated.

Next, an example of an operation of coating the coating material on the carbonaceous substance will be described.

The carbonaceous material is preheated to 100-120 ° C and charged into a hot mixer.

The high softening point pitch is mixed with a diluent such as creosote oil to prepare a liquid at 80 to 90 ° C., and then a predetermined amount of the fine powder is added and mixed. Although the mixing ratio of the high softening point pitch and the diluent depends on the properties of the high softening point pitch, usually, the high softening point pitch / diluent weight ratio = 70/30 to 95 /
It is preferable to set the range to 5.

A predetermined amount of the mixed solution (high softening point pitch + fine powder + diluent) prepared in the above is charged into the hot mixer and kneaded with the carbonaceous substance in the mixer to perform coating.

The kneading time is not particularly limited, but usually needs to be longer as the amount of the diluent added is larger. Note that substantially all of the diluent volatilizes during the coating operation.

Examples of the refractory material other than the carbonaceous substance acting on the carbon-containing refractory of the present invention include oxides such as magnesia, spinel, calcia, dolomite, alumina, silica, zirconia, and zircon; Oxides can be mentioned, and these are not particularly limited and vary depending on the purpose of use, but oxides mainly composed of magnesia, dolomite, spinel, and alumina are preferable.

The carbon-containing refractory of the present invention is prepared by mixing a coated carbonaceous substance and a refractory material having a controlled particle size at a predetermined compounding ratio, and bonding an organic resin having a large residual carbon content such as tar, pitch, petroleum pitch, and phenol resin. One or two or more of the agents are added, kneaded, and then press-molded, and 100 to 500
By drying or heat-treating to about ° C, an unfired refractory can be obtained, or it can be fired in a reducing atmosphere at about 700 to 1500 ° C and used as a fired refractory.

[Example] Example The carbon-containing refractory of the present invention will be further described below with reference to examples.

Example 1 First, 93 parts by weight of a high softening point pitch having a softening temperature of 150 ° C. and 7 parts by weight of creosote oil were mixed to form a liquid.
Fine powders of the kind and amount shown in the table were added and kneaded to obtain a coating material. Next, the obtained coating material was previously added to and mixed with scaly graphite heated to 105 ° C. in a hot mixer to obtain coated scaly graphite. The same operation was carried out using a mixture obtained by mixing 80 parts by weight of a high softening point pitch having a softening temperature of 320 ° C. and 20 parts by weight of creosote oil to form a liquid.

Next, 3 parts by weight of a phenol resin was added as a binder to the mixture having the compounding ratio shown in Table 2 using the coated scale graphite obtained as described above, and 1500 kg of the obtained compound was added. It was press-molded to a size of 230 mm × 114 mm × 65 mm at a pressure of / cm ² and dried at 200 ° C. for 24 hours to obtain a carbon-containing refractory. Various properties of the obtained carbon-containing refractory are also shown in Table 2.

[Effects of the Invention] The carbon-containing refractory of the present invention can provide excellent oxidation resistance because it uses a carbonaceous substance coated with a coating material comprising a high softening point pitch and a fine powder.

Claims (1)

(57) [Claims] 1. One or more fine powders previously selected from the group consisting of nitrides, carbides or borides other than boron carbide, metals and alloys per 100 parts by weight of high softening point pitch
3-50 parts by weight of carbonaceous material coated with a coating material having an addition ratio of 10-300 parts by weight and a refractory material
A carbon-containing refractory comprising 50 to 97 parts by weight.